const fs = require('fs');

// Get CLI params
const sqlJsonPath = process.argv[2];
const outputType = process.argv[3];
const outputFilePath = process.argv[4];

// Show generic CLI syntax error with usage
const showCommandError = () => {
  console.log(`
    Command syntex incorrect!

    Usage example;

    node parsqlres.js data.json --json [or --csv] output.json
  `);
};

// Proceed only if SQL JSON file is provided
if (sqlJsonPath) {
  // Extract data file contents
  const sqlJson = JSON.parse(fs.readFileSync(sqlJsonPath));
  const sqlAxis = sqlJson.axis;
  const sqlData = sqlJson.data;

  // Process data based on output type
  switch (outputType) {
    //  If output type is JSON
    case '--json':
      // Iterate over data array and create
      // JSON object for each array item
      const parsedJson = sqlData.map((dataItem) => {
        const record = {};

        // Create key-value pairs from column
        // and data
        sqlAxis.forEach((column, index) => {
          record[column] = dataItem[index];
        });

        // return map object
        return record;
      });

      // Write JSON array to output file path
      // `null` is replacer function
      // `2` is for spaces to use for indentation in file
      // `utf-8` is for file encoding
      fs.writeFileSync(outputFilePath, JSON.stringify(parsedJson, null, 2), 'utf-8');
      break;

    // If output type is CSV
    case '--csv':
      // Open stream to write file with `a` flag for appending contents
      const csvWriter = fs.createWriteStream(outputFilePath, { flags: 'a' });

      // Write column names enclosed in quotes and separated by comma
      csvWriter.write(sqlAxis.map(column => `"${column}"`).join(',') + '\n');

      // Iterate over each data item
      sqlData.forEach((dataItem) => {
        // Write data values enclosed in quotes and separated by comma
        csvWriter.write(dataItem.map(column => `"${column}"`).join(',') + '\n');
      });

      // Close stream
      csvWriter.end();
      break;

    default:
      showCommandError();
      break;
  }
} else {
  showCommandError();
}